HAGIA SOPHIA, officially the GREAT MOSQUE of AYASOFYA and formerly the CHURCH of HAGIA SOPHIA, is a Late Antique place of worship in ISTANBUL.
 Built in 537 as the patriarchal cathedral of the imperial capital of CONSTANTINOPLE, it remained the main cathedral of the Eastern Roman (Byzantine) Empire until 1453, when it was converted into an Ottoman mosque upon the fall of the city.
   In 1931 it became a secular museum, and on July 10, 2020 it will re-open as a mosque.
   Completed during the reign of the eastern Roman emperor JUSTINIAN I, it was then the world's largest interior space and among the first to employ a fully pendentive dome.

   It is considered the epitome of Byzantine architecture and is said to have „changed the history of architecture". It has been a UNESCO World Heritage Site since 1985 (Wikipedia).